1. Field of the Invention
The present invention relates to an internal combustion engine control device having an exhaust gas recycle system which recycles part of exhaust gas of the internal combustion engine again into an air intake pipe of the engine, and which has a trouble detect device.
2. Description of the Related Art
Conventionally, the above-mentioned trouble detect device for an exhaust gas recycle (which is hereinafter referred to as EGR for short) device is disclosed in, for example, Japanese Patent Unexamined Publication No. Sho. 52-27922 and No. Sho. 62-51746, in which the variations of the flow rates of the EGR when the recycling of the exhaust gas is present or absent are detected by use of a negative pressure detector provided in the air intake pipe to thereby detect troubles in the EGR device.
Also, as disclosed in Japanese Patent Unexamined Publication No. Sho 56-165756, a pressure obtained from a proper quantity of EGR flow rate under a given condition, which is previously stored, is compared with a detect pressure obtained from an actual EGR flow rate to thereby detect a trouble in the EGR device, if any.
Each of these conventional devices includes pressure detect means as detect means for detecting the EGR flow rate.
Referring now to FIG. 9, there is shown a block diagram of a conventional trouble detect device for an EGR device. In FIG. 9, an electronic control unit 22 performs a fuel control, an engine idle speed control and the like.
The fuel control means is used to calculate a basic amount of fuel on the basis of information obtained from an air flow sensor 25 as well as the number of revolution information obtained from an igniter 14 and an ignition coil 13.
Next, there is added to the above basic amount of fuel a correction value obtained from a water temperature sensor 17, which shows the warming-up condition of an engine 1, and other similar devices to thereby find the amount of fuel that corresponds to the state of the engine. The amount of fuel that corresponds to the thus calculated amount of fuel is supplied from an injector 5 to the engine 1.
An air flow sensor 25 is a Karman's vortex street type air flow sensor which measures a volumetric flow rate as a quantity of air detected. Accordingly, as shown in FIG. 10, the air flow sensor 25 includes therein an air quantity detect section 25a, an intake air temperature sensor 25b, an intake air temperature/air quantity correct section 25c, an atmospheric air pressure sensor 25d, an atmospheric air quantity correct section 25e and an air quantity signal output section 25f. In particular, in the air flow sensor 25, on the basis of information from the air quantity detect section 25a, intake air temperature sensor 25b, intake air temperature/air quantity correct section 25c and atmospheric air pressure sensor 25d, the quantity of air is calculated and the calculated quantity of air is then corrected by the air pressure air quantity correct section 25d. Thereafter, the thus calculated and corrected quantity of air is converted by the air quantity signal output section 25f into a mass flow rate which is actually sucked into the engine, and the air quantity signal output section 25f then outputs to the electronic control device 22 a signal which corresponds to the converted actual mass flow rate.
When a vane type air flow sensor is used as the air flow sensor 25, similarly, the correction by the atmospheric pressure sensor is generally enforced and thus to the electronic control system 22 there is supplied a signal which corresponds to the flow rate after the correction.
As mentioned above, some of the air flow sensors require the atmospheric air correction. The requirement depends on the kinds of air flow sensors 25. Thus atmospheric air correction may be performed by provision of the atmospheric pressure sensor 25d separate from the air flow sensor 25 or by having the atmospheric pressure sensor 25d within the air flow sensor 25.
Further, an idle speed control device checks the engine 1 for its idle state on the basis of information from an idle switch 9, which indicates whether a throttle valve 7 is in its fully closed state or not, as well as information from a vehicle speed sensor 18 which decides whether a vehicle is stopped or not, that is, by use of combination of the idle switch 9 and speed sensor 18.
If it is decided that the engine 1 is in its idle state, then the idle speed control device, responsive to the idle state of the engine 1 and, for example, in accordance with a signal 19 which indicates a load state of an air conditioning apparatus (which will be hereinafter referred to as an air conditioner), bypasses a throttle valve 7 and controls an ISC valve 10 to thereby vary the quantity of an air to be sucked into the engine 1, that is, the idle speed control device controls the number of revolution of the engine by means of the variations of the quantity of the intake air.
Here, since the quantity of air necessary for the idle state varies in the air density thereof according to the altitude, the quantity of air is corrected in accordance with the altitude. This requires an atmospheric pressure sensor 25d which is used to detect the altitude.
As mentioned above, in the control device of the internal combustion engine, there is provided the atmospheric pressure sensor 25d to secure a necessary control accuracy and a correction is enforced in accordance with a signal from the atmospheric pressure sensor 25d.
Now, in FIG. 9, there are an air intake pipe 3, an intake manifold 4, a pressure sensor 6 being used to detect the pressure of the air intake pipe 3 and to output a detection output to the electronic control unit 22, a throttle opening degree sensor 8, a recycle valve 11 being provided in an exhaust gas recycle passage interposed between an air exhaust pipe 15 and the air intake pipe 3, a passage area control actuator 12 (which is hereinafter referred to as an EGR solenoid), a battery 20, an ignition key switch 21 being connected in series to the battery 20, and an alarm lamp 23 being driven by the electronic control device 22. In addition, a surge tank 24 is provided.
Since the conventional trouble detect and diagnosis device of the exhaust gas recycle device is constructed in the above-mentioned manner, it is necessary to detect the pressure in order to detect the EGR air and also the atmospheric pressure sensor 25d is added separately from sensors which are used in the control device of the internal combustion engine.
Also, in the conventional control device of the internal combustion engine, due to the fact that the atmospheric pressure is detected and the amount of control is corrected according to the detected atmospheric pressure, there is provided the atmospheric pressure sensor 25d for detection of the atmospheric pressure.
Namely, in the conventional internal combustion engine control device having the exhaust gas recycle system which has the trouble detect device, there must be provided two kinds of sensors, that is, the pressure sensor 6 and atmospheric pressure sensor 25d, which results in the increased costs of the whole device.